1. forewarn. Warn,caution,admonish imply attempting to prevent another from running into danger or getting into unpleasant or undesirable circumstances. To warn is to speak plainly and usually in strong terms: to warn him about danger and possible penalties. To caution is to advise about necessary precautions, to put one on one's guard about possibly harmful circumstances or conditions, thus emphasizing avoidance of undesirable consequences: to caution him against driving in such weather.Admonish suggests giving earnest, authoritative advice with only tacit references to danger or penalty: to admonish a person for neglecting his duties.

warn

v.

Old English warnian "to give notice of impending danger," also intransitive, "to take heed," from West Germanic *warnojanan (cf. Old Norse varna "to admonish," Old High German warnon "to take heed," German warnen "to warn"); related to Old English wær "aware, cautious" (see wary). Related: Warned; warning.